Description: Shell of average size for the genus. The smallest adult observed measures 12 mm in largest diameter, the biggest shell observed measures 20.9 mm in largest diameter. Adult shells are about as high as broad. The body whorl is very broad when compared to most other species of Neripteron. Seen from the apertural side, it sticks out on the left side. The aperture is very large and covered with a thick whitish or yellowish callus, which extends on both wings. This callus is thickened on the columellar side of the aperture and also just before the parietal side. This thickening inside the outer lip is apparently an easy distinguishing characteristic on the species level. The columellar area is wide, the parietal teeth are set on a quite straight, not very curved area, and number 7 to 9, the lower ones are the smallest. The wings on top are thinner in shape compared to the big wings on the base of the shell, both wings are curved backwards. The colour of the external shells varies from black to speckled with grey spots. In one specimen (paratype 20) the colour of the outside is eroded, and the remaining pattern is a mixture of cream, black and purple. There is quite some variation in the different shells, as well in shape as in colour patterns. We refer to the plates for more understanding of this variation. The operculum is white to grey in colour, classic for the genus, with a paucispiral design on the flat side, the back-side with a raised extension, thin at the base, broader as it is more distant from the operculum proper, and with a tendency to split into two. This is typical of the genus, but the extension in the holotype is quite big when compared to other Neripteron.

Comparison: We compare N. leyteensis sp. nov. with other Neripteron that have a superficial resemblance to the new species:

*Neripteron cariosum (Wood, 1828): From the Hawaiian islands. This species is bigger than the new species: adult shells are between 17 and 25 mm in biggest diameter. At first sight this species looks identical and the variation in pattern is almost the same: from entirely black to speckled with grey flecks. However, in N leyteensis sp. nov. these flecks can be quite big and triangular in shape. Details that differ: the parietal teeth are more developed in N leyteensis sp. nov. and in adult specimens there is a considerable thickening of the shell, seen as a thick callus inside the shell, before the sharp lip. This is not seen in any of the shells of N cariosum we saw in the literature.

* Neripteron dilatata (Broderip, 1832): From French Polynesia: Tahiti and Moorea. The body whorl has got a much sharper "top"-spire and the upper wing has got a different shape than the lower wing: both wings are not pointing backwards as it is the case in adult and well developed N leyteensis sp. nov. The pattern is different: an extensive network of small triangular tents all over the shells in N dilatatum.

* Neripteron mauriciae (Lesson, 1831): From Mauritius Island, reaches a larger size. The wings in this species are usually not so well-developed, and if they are, they do not bend much backwards. The shape is more elongate in this species. The interior of the aperture is darker and the parietal teeth are more obvious. The latter characteristics will distinguish this species at once from the newly described one. Most specimens we could see in photographs are black coloured, and if patterned the pattern is not the same as in N leyteensis sp. nov.

* Neripteron taitense (Lesson, 1831): From Tahiti, the Marquesas, Samoa and Vanuatu. This species is uniformly olive black to black coloured and the wings are less developed than in the new species described herein. Inside the aperture is dark coloured and the callus in the aperture is not thick and white. The parietal teeth are small in both species, but the area where these teeth are is more curved in N taitense.

Type locality: The Philippines. Leyte. Padre Burgos. San Juan River. Distribution: At present only known from the type locality.